The present invention relates to pumps or analogous machines in general, and more particularly to improvements in submersible glandless motor pumps and analogous machines which can be used, for example, in nuclear reactor plants to circulate a coolant or another fluid medium. Still more particularly, the invention relates to improvements in systems for sealing the passage which is provided in a wall or the like and serves to allow an electrical conductor to pass from a higher-pressure area at one side of the wall to a lower-pressure area at the other side of the wall, e.g., to connect a motor within the confines of the pump housing with an external source of electrical energy.
The commonly owned copending application Ser. No. 339,071 of Schneider et al. discloses a system wherein an opening or passage in a wall which separates the interior of the housing of a submersible motor pump from the surrounding atmosphere is normally sealed (a) by an annular seat which is placed against a shoulder in the opening or passage and (b) by an insulating sleeve which surrounds an elongated electric conductor serving to connect an external source of electrical energy with a consumer, such as an electric motor in the plenum chamber which is constituted by the housing of the submersible motor pump. The conductor has a larger-diameter portion which is normally embedded in the material of the sleeve but can move into direct sealing engagement with the seat, not unlike the valving element of a check valve, when the sleeve is destroyed so that the pressure differential between the interior of the housing and the surrounding atmosphere can cause the enlarged portion of the conductor to move into sealing engagement with the seat. The seat can constitute a discrete component or an integral part of the wall.
The system of Schneider et al. ensures a highly satisfactory insulating action because it allows for the selection of wall thicknesses of insulators within a wide range. Moreover, the just discussed system renders it possible to ensure the establishment of a reliable sealing action in the event of overheating, i.e., in the event of destruction of the insulating components of the system, because this enables the conductor to move its larger-diameter portion into sealing engagement with the seat in the housing which separates the higher-pressure area from the lower-pressure area. Therefore, the system of Schneider et al. can be used with advantage in, or in combination with, pumps which are employed in nuclear reactor plants where partial damage to or complete destruction of the insulator means should not permit penetration of contaminated fluid into the surrounding atmosphere. Moreover, the system of Schneider et al. can be readily designed in such a way that eventual destruction of insulator means cannot entail any damage to or breakage of the cables which connect the ends of the conductor with a consumer of electrical energy and with a source of electrical energy. Thus, the elasticity and/or length of the cable, which latter must be extended in response to destruction of the insulation and ensuing travel of the larger-diameter portion of the conductor into sealing engagement with the seat, is selected with the view to ensure that such travel of the conductor will not entail any damage to the cable itself and/or to the connection between the cable and the conductor. Still further, the cross-sectional area of the cable and/or conductor and/or insulator can be readily selected in such a way that the insulator is not subjected to excessive mechanical stresses which could entail premature destruction of the insulator as a result of pressure against the seat and/or as a result of pressure of an embedded enlarged portion of the conductor against the surrounding portion of the insulator.
In many instances, e.g., when a glandless circulating pump is used in the boiler of a hydro-cracking reactor, the pressure in the region of the passage between a higher-pressure area and a lower-pressure area can rise to or even above 400 bar. The potential differences can amount to 10,000 volts and the maximum temperature of fluid which is to be confined within the higher-pressure area is determined by permissible temperature of the motor windings (normally in the range of 60.degree. C.).